Ballast apparatus



March 5, 1963 F. P. EPPERT BALLAST APPARATUS Filed April 20, 1961 United States Patent 3,0365% BALLAST APPARATUS Franklin 1. Eppert, Danville, Hi5, assigno'r toGenera1= Eiectric Company, a corporation of New York Fiied Apr. 20, E61, SE51. No. 104,3d8 12 Claims. (Cl. 315-277) My invention relates to ballast apparatus for starting and operating gaseousdischarge' devices such as fluorescent lamps and more particularly to a ballast apparatus for operating a plurality of fluorescent lamps.

In many fluorcscent'l'am'p applications, it is desirable that three or more high output fiuorescentlarnp's' be on erated from a single ballast apparatus. A principal drawback to the widespread adoption of such ballasts'in industry has been the restriction imposed on maximum voltage between any two leads of a ballast apparatus.

In order to obtain approval of the Underwriters Laboratories, the voltage between any two leads of such' a baliast cannot exceed 600' volts by more than IO'per'ce'nt at the rated line voltage. For example, the lamp starting requirements for three 72 inch T12 high output lamps in series is approximately 600 volts at uated' line for four such lamps in series the starting requirement would be approximately 800 volts at rated line voltage. Also, the starting voltage requirement for three 96 inch T12 high output fluorescent lamps in series exceeds by more than percent the 600 volt requirement of the Underwriters Laboratories. I

It is a further requirement that the ballast apparatus provide a peak starting potential of 700. volts.- This peak voltage is required in order to cause the gas in the vicinity of the one of the lamp electrodes to ionize and thereby make it possible for the lamp to be started at 'a lower open circuit R.M.S. (Root Mean Square) voltage. From a manufacturing and a cost standpoint, it is also desirable that the ballast apparatus employ st-a'ndar'd'core punchings to eliminate the need'for new dies and' for a redesign of the magnetic circuit.

Accordingly, it is a principal object of my invention to provide new and improved ballast apparatus for starting and operating a plurality of fluorescent lamps.

It is another object of my invention to provide anew and improved ballast apparatus for operating three or more lamps wherein the R .M.S. voltage between any two leads of the ballast apparatus will not exceed by more than ten percent 600 volts at the rated input voltage.

A further object of my invention is to provide a new and improved ballast apparatus that is economical to manufacture.

Briefly stated, in accordance with one aspect of my invention, I have provided a ballastappara tus havingtwo magnetic cores, each having a primary winding and a secondary winding inductively coupled therewith and one of the magnetic cores having a crossover winding inductively coupled thereon. The crossover winding is in the magnetic circuit of one of the magnetic cores but is connected in the electrical circuit of the windings indpgtively coupled on the other magnetic core. It was found that the crossover winding provided a balance between the R.M.S. open circuit voltage requirements and peak starting voltage requirements of the lamp circuits associated with the two ballast cores.

"In another aspect of the invention, a first capacitor is connected in series circuit relationship with the first secondary winding in the first lamp circuit and a second capacitor is connected in series circuit relationship with the second secondary winding in the second lamp circuit. Thus, since both lamp circuits draw a leading current, a lead-lead-ballast circuitarrangemcnt is provided for starting and operating a plurality of lamps. Although 3,19%,565 Patentednot necessary, if desired, the capacitors maybe housed in a single capacitor case. I II I II The subject matter which I regard as my invention is particularly pointed out and distinctively claimed in the concluding portion of this specification. My invention, however, both as to organization and method of operation together with further objects and advantages thereof may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which: I I

FIG. 1 is a schematic circuit diagram of a ballast apparatus embodying my invention; 7

FIG. 2 is a plan viewof the ballast apparatus included in the circuit ofFIG. 1' showing the components with the circuit connections being omitted; and I I FIG. 3 is a schematic circuit diagram of a ballast apparatus for operating four lamps illustrating another embodiment'of the invention. I I I I Referring now to the embodiment of the invention illustrated in FIG. 1, a ballast apparatus is generally identified by the reference numeral I O'a nd is shown enclosed in the dashed rectangle which schematically represents the ballast case 11. The ballast apparatus 10 includes a first high reactancetr-ansfonner 12' having a magnetic core 13, a magnetic shunt 14', a primary winding 15 and a secondary winding 16 and also includes a second high reactance transformer 17 having a magnetic core 18, a magnetic shunt 19, a primary winding 29, a

, secondary Winding 21 and a crossover winding '22 The crossover winding 22 is in the magnetic circuit of the high reactance transformer 11 and is-inductively coupled with primary winding 21}. However, it will be noted that electrical lead 23 connects the crossover winding 22 in series circuit relationship with high reactance transformer 12. Thus, the'crossover winding'22 is inductively coupled on one high reactance transformer 17 but is connected in the electrical circuit of the other high reactance transformer 12. I

A pair of input terminal leads 24, 25 are provided for the purpose of connecting theballast apparatus 11 to a suitable alternating current supply (not shown) such as a 60 cycle, volt alternating current supply. As shown in FIG. 1, primary winding 15 is connected directly across the input terminal leads 24, 25 and electrical leads 26, 27 connect primary winding 2 of high reactance transformer 17 across input terminal leads 24, 25.

Therclative directions of the open circuit or generated voltages in the windings of the high reactance transformers 12, 17 are indicated by the arrows next to the respective windings. it will be noted that the primary winding 15 and the secondary winding 16 of high reactance transformer 12 are connected in autotransformer relationshihp and secondary Winding 16 is so arranged that it is additive to thevoltage across the primary winding15. The crossover winding 22', which is connected in series circuit relationship with secondary winding 16, is so arranged on the magnetic core 18 of the high reactance transformer 17 so that voltageinduced by the crossover winding 22 is in additive relationship to the voltage across secondary winding 16. Thus, the Voltages across the crossover winding 22, secondary winding'16 and primary'winding 15 are in am adding relationship and the combined voltages are applied by means of the electrical leads Z8, 29, 30 across a serially-connected pair of fluorescent lamps 1, 2.

Lamps 1, 2 may be positioned in close proximity to a conductive fixture 31 so that lamps 1, 2' are" in capacitive relationship therewith. The conductive fixture 31 preferably is of the same potential as the low'potentialinput lead 25 which is provided for connection to the grounded side of the power supply. Since it is generally required assesses 3 that the conductive fixture 31 be grounded, it may be desirable, but not necessary, to connect the low potential side of the primary winding 15 to the ballast transformer case it through a high ohma-ge resistor (not shown) as is well known in the art.

High reactance ballast transformer 17 is connected in circuit with lamp 3 by electrical leads 29, 32 and the output of transformer 17 is applied across lamp 3. Lamp 3 is also located in close proximity to a grounded fixture 36 which normally would be the same fixture to which lamps 1 and 2 are capacitively coupled if lamps 1, 2, 3 are installed in a single fixture. The primary winding 15 of high reactance transformer 12 is connected in parallel circuit relationship with primary winding 2t and the full input voltage is applied across both of the primary windings 1.5, 2%. It will be appreciated, of course, that the primary windings in some applications may, if desired, be connected in series circuit relationship.

A power factor capacitor 34 provides sufficient capacitive reacta-nce as compared to the inductive reactance of the high reactance transformer 12 to draw a leading current through the secondary winding 16. Similarly, a power factor capacitor 35 is connected in series circuit relationship with the secondary winding 21. It is to be understood, however, that either power factor capacitor 34, 35 may be omitted if it is desirable to operate one of the lamp circuits associated with either of the high reactance transformers 12, 17 as a lag circuit.

in order that the cathodes of lamps 1, 2, 3 may be con tinuously supplied with a low current during operation, cathode heating windings 37, 3d are closely coupled with the primary winding 15 and are connected in circuit with cathodes 45, 36, 4-3, 49 of lamps 1, 3 by means of electrical leads 3t), 33, 44 and 41, 42, d3. Cathode heating windings 39, 4d are closely coupled with primary winding 2th and are connected in circuit with cathodes i7, 563 of lamps 2, 3 by means of electrical leads 51, 52., 53, 54. A starting capacitor 3 is connected across leads 28 and 42 so that the starting voltage is first applied across lamp 1.

From the foregoing description, it will be seen that each of the high reactance transformers l2, 17 have a lamp circuit associated therewith, one of the lamp circuits including lamps 1 and 2 and the other circuit including lamp 3. Each high reactance transformer l2, 1''! provides the current limiting impedance required in its respective lamp circuit because of the negative resistance characteristics of the lamps Ll, 2, 3. As will hereinafter be more fully explained, the lamp circuits are sequentially started, the lamp circuit connecting lamps l, 2 in electrical circuit with the crossover winding E2, secondary winding l6 and primary winding lo" being the first to start.

As shown in FIG. 2, the high leakage reactanee transformers 12, 1'7 are disposed in an end-to-end relationship in a ballast case 11. For the sake of clarity, the circuit connections shown schematically in PEG. 1 have been omitted. It will be noted that magnetic cores l3, 18 of the transformers l2, 17 are identical in configuration. Magnetic core 13 is a shell type core having a T-shaped central winding leg 55 and yoke sections 56, 57 disposed at each side of the central winding leg d to form a closed magnetic circuit. Similarly, magnetic core 1? has a T-shaped central winding leg 5% and yoke sections 59, 6t} disposed at each side of central winding 55 to form a closed magnetic circuit. The space between the yoke seclions and central winding leg of magnetic cores l3, 18 is provided to accommodate coil assemblies e1, 62, as, 64. The central winding legs 5'5, 53 and the yoke sections 56, 57, 59, 60 are comprised of a stack of laminations stamped from a continuous strip of electrical steel. The adjacent ends of magnetic cores l3, 18 are insulated by a cardboard separator 65.

A three terminal capacitor assembly containing capacitors 34, 35 provides the capacitive reactance required to cause a leading current to flow in the secondary windings 4 '16, 21. It will be noted that in the schematic diagram shown in MG. 1, the capacitors 34, are schematically illustrated as two separate capacitors. As shown in the plan view of FIG. 2 the capacitors 34, 35' are housed in a single capacitor case 66.

Coil assembly 61 includes primary winding 15 and cathode heating windings 37, 38 which are closely coupled with primary winding 15 and coil assembly 63 includes primary winding 2% and cathode heating windings 3%, 4t Secondary winding 16 is included in coil assembly as, while the secondary winding 21 and the crossover winding 22 are included in coil assembly 64. In accordance with the usual practice all of the components of the ballast apparatus to are potted in a suitable potting con pound.

Since the primary windings 15, 2i? and the secondary windings 16, 21 are placed side-by-side on the central winding legs 55, 58, there is a certain amount of a leakage reactance in the magnetic circuit because of this arrangement. As shown in FIG. 2, an additional leakage reactance is provided in each of the high reactance transformer-s 12, 17 by including high reluctance flux leakage paths or magnetic shunts, la, 19 between coil assemblies 61, 62 and re, 64 respectively. It will be understood that depending upon the design of the high reactance transformer, flux leakage paths may be formed either through nonmagnetic material, such as air, or through magnetic material by the provision of projecting shunt legs integrally formed with the yoke sections or insertable shunts such as are employed in the illustrated embodimerit of the invention.

Referring now to FIG. 3, a ballast apparatus 7% utilizes a pair of high reactance transformers 12, 17 which are employed in a substantially similar circuit configuration to the one shown in FIG. 1. Accordingly, I have iden' titled the corresponding parts thereof by the same reference numerals. Input terminal leads 24, 25 are provided for connecting ballast apparatus 7% to an alternating cur rent supply such as a volt, 60 cycle alternating current supply.

As shown in FIG. 3, ballast apparatus 7% is contained in a ballast case 71 represented schematically by the dashed rectangle. Primary winding 15 of high reactance transformer 12 is connected across terminal input leads 24, 25. Electrical leads 26, 27 connect primary winding 2d across terminal input leads 2%, 25 so that the primary windings 15, 2t! are connected in parallel circuit relationship. Primary winding 15 and secondary winding 16 are inductively coupled in the magnetic core 15. Primary winding 2d, secondary winding 21, and crossover winding 22 are inductively coupled on magnetic core 18. The crossover winding 22 is connected in series circuit relationship with secondary winding 16 and is thereby connected in the electrical circuit of high rea-ctance transformer l2. Flux leakage paths are provided in the magnetic circiuts of transformers 12, 17 by magnetic shunts 1d, 19 respectively.

In the circuit shown in FIG. 3, the output of high reactance transformer 12 is applied by electrical leads 28, 29 across a pair of serially conuecteo lamps d, 5 disposed in capacitive relation with grounded conductive fixture 68. The output of the other high reactance transformer 17 is applied to a second pair of serially connected lamps a, '7 disposed in capacitive relation with a grounded conductive fixture o The ballast apparatus I'll was intended for operation of two dissimilar pair of lamps, such as a pair of 96 inch Tl2 high output rapid start lamps and a pair of 72 inch T12 high output lamps. The lamps c 5 are higher output than lamps e, '7' and are represented as being or greater length than lamps d, 7. it will be understood, of course, that other combinations of lamps can be operated by ballast apparatus 7%.

Power factor capacitors 34, 35 are connected in series circuit relationship with secondary windings i6, 21 respectivel". T he power factor capacitors e5 introduce sulilcient capacitive reactance in the secondary circuits of high reactance transformers 12, 17 so that a leading current is caused to flow through secondary windings 16, 21. in each lamp circuit a starting capacitor 72, 73 is connected across one of the lamps. Thus, capacitor 73 is connected in circuit across lamp 5 while capacitor 72 is connected in circuit across lamp 7. The starting capacitors 72, 73 function in the usual manner to cause the open circuit voltage to be applied initially across the lamp which is not shunted by the starting capacitor 72, 73. When this lamp is ignited, the voltage across the starting capacitors 72, 73 is sufiicient to start the shunted lamp.

After both lamps are started the impedance of a starting capacitor is such that no significant current will fiow through it.

Cathode heating windings 37, 38, 39, 40, 74 continuously supply lamps 4, 5, 6, 7 with cathode heating current. Cathode heating winding 38 is an extension of the primary winding and is connected in circuit with cathodes 43, 78 oflamps 4, 6 by electrical leads 43, 44-, 23, 3t), 33. Cathode heatingwinding 37'is also closely coupled with primary winding 15 and is connected in circuit with cathodes 45', 46 oflamps 6, 7 by electrical leads 41, 42. 'Similarly, cathode heating windings 39, iii, 74 are closely coupled with the primary winding of high reactance transformer 17. Electrical leads 75, 76 connect cathode heating winding 74 in circuit with cathodes 79, 80 of lamps d, 5. Cathode heating windings 39, are connected by leads 51, 52, 53, 5- with cathodes 47, 81 of lamps 5, 7.

The operation of the ballast apparatus 10 shown in FIG. 1 will now be more fully described. When the input tcrminalleads 24, 25 are connected to a suitable alternating current supply, the line voltage is applied across the primary windings 15, 20 and voltages are induced in the secondary windings 16, 21, crossover winding 22 and the cathode heating windings 37, 33, 39, 40. All of the cathodes of lamps 1, 2, 3 are instantly supplied with heating current. Initially the peak and R.M.S. starting voltage across leads 29 and 32 developed by transformer 17 is insufiicient to start lamp 3. However, the peak and R.M.S. voltage developed by high reactance transformer 12 and across crossover winding 22 of high reactance transformer 17 is of sufiicient magnitude to start lamp l.

After lamp 1 has ignited, the voltage across the starting capacitor 8 is applied across lamp 2, and is suficient to start lamp 2. When lamps 1 and 2 are ignited, the impedance of the starting capacitor 8 prevents any appreciable current flow through it because lamp 2 provides a lower impedance path. Further, a leading current iiows in'the crossover winding 22 because of the capacitive reactance introduced in the secondary circuit of high reactance transformer 12 by the power factor capacitor 34. It was discovered that this leading current in crossover winding 22 causes the peak voltage and RMS open cir cuit voltage across the output leads 29, 32 of high reactance transformer 17 to increase and to attain a mag nitude sutlicient to start lamp 3. After lamp 3 is started, the output of the high reactance transformer 17 is sulficient to operate lamp 3.

In accordance with the invention, I have provided a ballast apparatus 16 in which first and second lamp circuits are sequentially started, the first lamp circuit being started by the voltage provided by a first high reactance transformer 15 and a crossover winding 22 inductively coupled in a second high reactance transformer 17 associated with the second lamp circuit. When the lamps 1, 2 of the first circuit are started, the leading current flowing through the crossover winding 22 causes the peak voltage and R.M.S voltage voltage in the second lamp circuit to.

rise thereby starting the lamp or lamps in the second lamp circuit. It will be appreciated that the individual lamp circuits may be designed to start and operate two or more lamps.

The operation of the ballast apparatus '76 shown in" FIG. 3 is substantially similar to the ballast apparatus 16 6 of FIG. 1. When the input terminal leads 24-, 25 are energized, the peak and R.M.S. starting voltage provided by high reactance transformer i2 is sufficient to start lamp 4. Once lamp 4 is started, the voltage across the starting capacitor 73 is sufiicient to start lamp 5 and a leading current to flow through the crossover winding 22 inductively coupled on the magnetic core 18 of high reactance transformer 1'7. This results in an increased peak and R.M.S. starting voltage across lamps 6 and 7, which is initially applied across lamp 6. After lamp 6 is ignited, the voltage across the starting capacitor 73 is sufiicient to ignite lamp 7. Thus, the lamp circuit containing lamps 4, 5 is the first to start.

As a specific exemplification of the invention, a ballast apparatus as shown in FIG. 1 was constructed for igniting and opera-ting a three lamp combination of 96 inch T12 or 84 inch T12 rapid start high output fluorescent lamps. The ballast apparatus utilized thefollowingcor'nponents which are cited by way of illustration:

Primary windings 15, 2t) 370 turns of .0285 inch wire. Secondary winding I 16 1500 turns of .0226 inch wire.

Secondary winding 21 1272 turns of .0226 inch wire. Crossover winding 22 228' turns of .0226 inch wire.

Cathode heating windings 37', 38 Cathode heating 13 turns of .0285 inch wire.

windings 39, 40 12 turns of .0285 inch wire. Capacitor 34 3.3 microfarads, 570 volts R.M.S. Capacitor 35 4.3 microfarads, 570 volts R.M.S. Capacitor 8 .06 microfarads.

In the foregoing. exemplifi'ca'tion of the invention, an R.M.S. starting voltage of 500 volts and a peak voltage of 840 volts was measured across leads 28 and 29 at a minimum input voltage. During the open circuit condition of the first circuit (lamps 1 and 2) an R.M.S. starting voltage of 400 volts anda peak voltage of 660 volts was measured across lampfi. Since a peak ionization voltage of 700 volts is required to start the lamps, lamp 3 did not initiallyignite. However, after lamps 1 and 2 were ignited, it was found that the leading current flowing in the crossover winding 22 improved the crest factor of the voltage output of the high reactance transformer 17 so that the peak ionization voltage across lamp 3 was increased to 730 volts, which is suific-ientto start lamp 3. Further, the open circuit voltage was increased to 413 volts R.M.S. Thus, lamp 3 in the second lamp circuit is ignited after lamps 1 and 2 are ignited.

It will be appreciated that the crossover winding arrangement of the invention makes it possible to accomplish with a pair of high reactance transformers what the several transformers cannot independently accomplish. Further, the ballast apparatus provides the important advantage that a magnetic core normally used for shorter lamps can be employed to operate longer lamps which heretofore could not be operated independently from the same magnetic core. Consequently, an economy is achieved in that existing magnetic core designs can be utilized eliminating the expense of a redesign.

It will be understood that while I have illustrated my invention by a specific exemplification thereof, the invention has general applicability to two core ballasts used to start and operatetwo or more lamps. Thus, the invention may be employed in ballast circuits used to start and operate five and six lamps. While the present invention has been described by reference to exempliiications thereof involving two lamp circuits for operating three and four lamps, it is to be understood that modifications may be made by those skilled in the art without actually departing from the invention. It is, therefore, intended in the apfall Within the tr e spirit and scope of accuses pended claims to cover all such equivalent variations th't the invention.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A ballast apparatus for starting and operating a plurality of gaseous discharge lamps from an alternating current supply, a first high reactance transformer having a first primary winding and a first secondary winding in ductively coupled on a first magnetic core, a second high reactance transformer having a second primary winding and a second secondary winding inductively coupled on a second magnetic core, a crossover winding inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuit relationship with the first secondary winding of the first high reactance transformer, said first and second primary windings being adapted for connection in circuit with said alternating current supply, a first circuit means including electrical leads for connecting at least one of said gaseous discharge lamps in a first lamp circuit so that the voltage across at least said crossover winding and said first secondary winding is applied across said lamp in said first lamp circuit and a second circuit means including electrical leads for applying at least the voltage across said secondary winding across at least one of said gaseous discharge lamps in a second lamp circuit.

2. A ballast apparatus for starting and operating a plurulity of arc discharge lamps comprising a first high reactance transformer having a first magnetic core, a first primary winding and a first secondary winding inductively coupled on said magnetic core, a second high reactance transformer having a second magnetic core, a second primary winding and a second secondary winding inductively coupled thereon, a crossover winding being inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuits relationship with said first secondary winding of said first high reactance transformer, a starting capacitor, a first circuit means for connecting at least a pair of serially connected lamps in a first lamp circuit so that at least the voltage across said crossover winding and said first secondary winding of said high reactance transiormer is applied across said serially connected lamps, said first circuit means including electrical leads for connecting said starting capacitor across one of said lamps, a second circuit means for connection with at least one lamp so that at least the voltage of said second secondary winding of said second high reactance transformer is applied to said lamp during starting and operation.

3. The ballast apparatus set forth in claim 2 wherein a capacitor is connected in series circuit relationship with at least one of said secondary windings to cause a eading current to fiow through said secondary winding.

4. The ballast apparatus as set forth in claim 2 wherein a first capacitor is connected in series circuit relationship with said secondary winding to cause a leading current to ficw therethrough and a second capacitor is connected in series circuit relationship with said second secondary Winding of said second high reactance ballast transformer to cause a leading current to flow through said second sccondary wind ng.

5. The ballast apparatus as set forth in claim 2 wherein the first primary winding of said first high reactance transformer and the second primary winding of said second gh reactance transformer are connected in parallel circuit relationship.

6 A ballast apparatus for operating a plurality of fluorescent lamps from an alternating current supply comprising a first high reactance transformer including a first magnetic core, a first secondary winding and a first primary winding inductively coupled therewith on said first magnetic core, a second high reactance transformer including a second magnetic core, a second primary winding and a second secondary winding inductively coupled therewith on said second magnetic core, a pair of input terminal leads for connection across said alternating current supply, said first primary winding and said second primary winding being connected across said input terminals, a crossover winding inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuit relationship with said first secondary winding, a first circuit means including electrical leads for connection with at least a pair of fluorescent lamps in a first lamp circuit and for applying the output of said first high tea-stance transformer across said lamps, and a second circuit means including electrical leads for connection across at least one fluorescent lamp in a second lamp circuit and for applying the output of said high rcactance transformer across the lamp in said second lamp circuit.

7. The ballast apparatus set forth in claim 6 wherein a capacitor is connected in series circuit relationship with at least one or" said secondary windings to cause a leading cur cut to flow therethrough.

8. T he ballast apparatus set forth in claim 6 wherein a first capacitor is connected in series circuit relationship with said first secondary winding to cause a leading current to how therethrough and a second capacitor is connected in series circuit relationship with said second secondary winding of said second high reactance ballast transformer to cause a leading current to Flow through said second secondary windin 9. The ballast apparatus set forth in claim 6 wherein a first power factor capacitor is connected in series circuit relationship with said first secondary winding and a second power factor capacitor is connected in series circuit relationship with said second secondary winding, said first power factor capacitor and said second power factor capacitor being housed in the same capacitor case.

1 3*. A ballast apparatus for starting and operating a plurality of gaseous discharge lamps from an alternating current supply, a first high reactance transformer having a first primary winding and a first secondary winding inductively coupled on a first magnetic core, a second high reactance transformer having a second primary winding a second secondary winding inductively coupled on a second magnetic core, sairl first and secondary primary windings being connected in parallel circuit relationship, a crossover winding inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuit relationship with the first secondary winding of the first high reactance transformer, fir and second primary windings being adapted for connection in circuit with said alternating current supply, a first circuit means including electrical leads for connecting at least one of said gaseous discharge lamps in a first lamp circuit so that the voltage across at least said crossover winding and said first secondary Winding is applied across lamp in said first lamp circuit and a second circuit means including electrical leads for applying at least the voltage across said secondary winding across least one of said gaseous discharge lamps in a second lamp circuit.

ll. A ballast apparatus for starting and operating a plurality of gaseous discharge lamps from an alternating current supply, a first high reactance transformer having a first pmary winding and a first secondary winding inductively coupled on a first magnetic core, a second high reactance transformer having a second primary winding and. a second secondary winding inductively coupled on a second magnetic core, a capacitor connected in series circuit relationship with at least one of said secondary windlugs, a crossover winding inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuit relationship with the first secondary winding of the first high reactance transformer, said first and second primary windings being adapted for connection in circuit with said alternating current supply, a first circuit means including electrical leads -for connecting at least one of said gaseous discharge lamps in a first lamp circuit so that the voltage across at least said crossover winding and said first secondary winding is applied across lamp in said first lamp circuit and a second circuit means including electrical leads for applying at least the voltage across said secondary winding across at least one of said gaseous discharge lamps in a second lamp circuit.

12. A ballast apparatus for starting and operating a plurality of gaseous discharge lamps from an alternating current supply, a first high reactance transformer having a first primary winding and a first secondary winding inductively coupled on a first magnetic core, a second high. reactance transformer having a second primary winding and a second secondary winding inductively coupled on a second magnetic core, a first capacitor connected in series circuit relationship with said first secondary winding to cause a leading current to flow therethrough, a second capacitor connected in series circuit relationship with said second secondary winding to cause a leading current to flow through said second secondary winding, a crossover Winding inductively coupled in the magnetic circuit of said second high reactance transformer and connected in series circuit relationship with the first secondary winding of the first high reactance transformer, said first and second primary windings being adapted for connection in circuit with said alternating current supply, a first circuit means including electrical leads for connecting at least one of said gaseous discharge lamps in a first lamp circuit so that the voltage across at least said crossover winding and said first secondary Winding is applied across said lamp in said first lamp circuit and a second circuit means including electrical leads for applying at least the voltage across said secondary winding across at least one of said gaseous discharge lamps in a second lamp circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,996,644 Nathanson Aug. 15, 1961 

1. A BALLAST APPARATUS FOR STARTING AND OPERATING A PLURALITY OF GASEOUS DISCHARGE LAMPS FROM AN ALTERNATING CURRENT SUPPLY, A FIRST HIGH REACTANCE TRANSFORMER HAVING A FIRST PRIMARY WINDING AND A FIRST SECONDARY WINDING INDUCTIVELY COUPLED ON A FIRST MAGNETIC CORE, A SECOND HIGH REACTANCE TRANSFORMER HAVING A SECOND PRIMARY WINDING AND A SECOND SECONDARY WINDING INDUCTIVELY COUPLED ON A SECOND MAGNETIC CORE, A CROSSOVER WINDING INDUCTIVELY COUPLED IN THE MAGNETIC CIRCUIT OF SAID SECOND HIGH REACTANCE TRANSFORMER AND CONNECTED IN SERIES CIRCUIT RELATIONSHIP WITH THE FIRST SECONDARY WINDING OF THE FIRST HIGH REACTANCE TRANSFORMER, SAID FIRST AND SECOND PRIMARY WINDINGS BEING ADAPTED FOR CONNECTION IN CIRCUIT WITH SAID ALTERNATING CURRENT SUPPLY, A FIRST CIRCUIT MEANS INCLUDING ELECTRICAL LEADS FOR CONNECTING AT LEAST ONE OF SAID GASEOUS DISCHARGE LAMPS IN A FIRST LAMP CIRCUIT SO THAT THE VOLTAGE ACROSS AT LEAST SAID CROSSOVER WINDING AND SAID FIRST SECONDARY WINDING IS APPLIED ACROSS SAID LAMP IN SAID FIRST LAMP CIRCUIT AND A SECOND CIRCUIT MEANS INCLUDING ELECTRICAL LEADS FOR APPLYING AT LEAST THE VOLTAGE ACROSS SAID SECONDARY WINDING ACROSS AT LEAST ONE OF SAID GASEOUS DISCHARGE LAMPS IN A SECOND LAMP CIRCUIT. 